Major advantage of bladder drainage after pancreatic transplant is the ability to monitor the patient for graft rejection. Decrease of more than 50% in urine amylase activity after pancreas transplantation signals possible acute rejection. The decrease in urinary amylase may be the only clinical indication of a problem, with no change in the serum concentration of creatinine or glucose or activity of serum amylase or lipase. Biopsy of pancreas is done to confirm diagnosis of rejection. Ref: Stem Cell Therapy for Diabetes By Shimon Efrat, Page 71